The present invention relates generally to the field of optical devices. In particular, the invention relates to flashlights.
Flashlights with a zooming, or focusing, function generally include a lens which can be moved relative to the light bulb. The lens can bend the light differently based on the distance between the lens and the light bulb. The amount of bending of the light by the lens depends greatly on certain properties of the lens, particularly the thickness of the lens. For increased zooming capability, a thicker lens may be required. However, the increased thickness of the lens results in a substantial increase in the weight of the flashlight. Also, thicker lenses typically have steeply curved surfaces, particularly in the perimeter regions, causing the light of different wavelengths to be refracted differently, resulting in a rainbow effect being produced. Thus, it is desirable to provide increased zooming capability while avoiding the above-described shortcomings.